Dune Research Articles

Devastation of the cerrado of mato grosso do sul and the advance of arenization in the pardo river watershed

Despite the significant biodiversity in the Cerrado, the process of occupation, subsequent economic cycles, and intensification of agriculture in a predatory manner have caused profound alterations in this biome. This study analyzed changes in land use and land cover in the Cerrado of Mato Grosso do Sul between 1985 and 2022 by mapping and also investigating the formation and dynamics of sand dunes in the Bauru sedimentary basin, focusing on the Pardo River watershed. MapBiomas Network data, collection 8, were used for land use and land cover analysis. Arenization foci cartography was conducted using brightness index 2 based on Sentinel-2 satellite images in Sentinel Application Platform software. The historical analysis of land use and cover in the Cerrado of Mato Grosso do Sul revealed a rapid transformation of the landscape, with a drastic reduction of native vegetation and an intensification of large-scale monocultures. Between 1985 and 2022, the Cerrado of Mato Grosso Sul lost 4.6 million hectares of native vegetation (forest formations, savannahs, grasslands, and wetlands), representing 24.54% of this territory. Recent changes in land use include pasture-soybean and pasture-eucalyptus. In the Pardo River watershed, arenization foci cover an area of 17,834.34 hectares, with varying dimensions ranging from less than 1 hectare to 376.41 hectares. The arenization process occurs in different slope compartments, such as the base, slope, and interfluves. The physical and chemical characteristics of Quartzipsamments, such as low organic carbon content in soil, are associated with high rates of surface exposure and weakened load-dependent structures, leading to degradation. Arenization occurs where natural vegetation has been suppressed and soil has been depleted by poorly managed production processes.

Geochemical characterization and reserve estimation of the economic heavy minerals of Sonadia Island, Bangladesh

The goal of the current study is to understand the elemental concentration, reserve assessment, mineralogical composition, and distribution of heavy minerals in the dune sands, foreshore, and backshore of Sonadia Island, Southeast Bangladesh. The study area yielded a number of drill hole composite sand samples that were used for density and magnetic separation of heavy minerals. These samples were then subjected to petrographic characterization, grain counting, mineralogical analyses using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM–EDX), x-ray diffraction (XRD), and bulk sand geochemistry using X-ray fluorescence (XRF). The results of heavy liquid separation show that the total heavy mineral (THM) enrichments in foreshore sand (about 4.86%), backshore sand (about 9.03%), and dune sand (about 22.28%) are significantly higher. After characterizing the sand samples from Sonadia Island based on the abundance of each mineral species, the average content values relative to total economic heavy minerals (TEHM) were determined to be 38.14% ilmenite, 5.74% magnetite, 51.52% garnet, 1.01% zircon, 3.57% rutile, and 0.01% monazite. An SEM–EDX examination reveals that the elemental concentration of ZrO2 in zircon is 66.60%, while the average TiO2 content in rutile is ~ 95%, whereas TiO2 is 45% and the total Fe2O3 is 45.70% in ilmenite. Major phases including amphibole (tremolite) 45.9%, muscovite 15.6%, quartz 12.6%, garnet (almandine) 10.9%, dolomite 7.9%, ilmenite 4.1%, and kaolinite 1.3% are also identified by the XRD pattern. There are an estimated 19,794 tons of garnet in the foreshore sand, 47,324 tons in the backshore sand, and 276,868 tons in the dune sand within the reserve, making it the most prevalent heavy mineral. Ilmenite is the second most common heavy mineral, with quantities detected in the foreshore (15,016 tons), backshore (30,487 tons), and dune sand (215,092 tons).

Influence of ground slag and dune sand behavior of binary and ternary cement

This study examines the effect of slag and dune sand replacement (binary and ternary) in cement production, focusing on key mechanical properties and chemical behavior, especially on fire loss and residual an insoluble examined at different curing times ranging from 2 to 210 days. The findings show that the addition of slag and dune sand powder significantly influences the mechanical and thermal properties of mortar mixtures replaced by slag the compressive strength increases up to 30% and a slight decrease up to 40 is observed %. Ternary mixes show improved long-term compressive strength, especially after 120, 210 days, although generally young strength is lower than control When binary and ternary are combined with high flexural strength, ternary mixes exhibit good long-term performance, especially in mixtures of 20-30% slag and 10% dune sand lime (ACHOURA, D and al. 2008). From a thermal perspective, the replacement of slag with dune sand lime reduces losses during combustion, indicating excellent thermal stability. The addition of dune sand lime increases the proportion of impervious residue, indicating stability and durability of the cement. Overall, the study concludes that the proper use of slag and dune sand lime especially in ternary mixes can significantly improve the long-term mechanical and thermal performance of cement mortars Thus these findings provide valuable insights for designing building materials with higher durability and strength to suit specific construction application applications.

Effect of Polypropylene Fibers on the Behavior of Dune Sand Concrete Subjected to Elevated Temperatures

In the field of civil engineering, concrete is one of the most used materials. Above a particular temperature, concrete can exhibit thermal instability during fire events. Improving the safety of buildings and structures is an important issue of this study. This paper investigates the effects of adding polypropylene fibers to dune sand concrete at high temperatures. Prismatic specimens (4 x 4 x 16 cm3) are produced, and stored until the concrete is hardened. The samples are then subjected to a heating-cooling cycle, starting from room temperature and increasing by 0.1 °C/min until reaching 600 °C. The length and the rate of polypropylene fibers are examined to determine their impact on compressive strength, porosity, and weight loss at temperatures of 80, 150, 300, 450, and 600 °C. Also, the partial replacement of dune sand (DS) with river sand (RS) is investigated. The results show that, for temperatures below 450 °C, the strengths of dune sand concretes varied from 29 to 39% compared to those obtained with concretes subjected to an ambient temperature (20 °C). However, it should be noted that residual compressive strength values decrease at most temperatures with the addition of polypropylene fibers. Furthermore, sand concrete with 50% DS and 50% RS shows an increase in compressive strength of 43.77% compared to that obtained by 100% DS concrete.

High ecostoichiometric stability and accumulating SiO2 and NO3− as main physiological adaptive mechanisms for reed to adverse environments

Previous studies have shown that nutrients accumulation played important roles in resisting to stress resistance of plants. Our study examined the ecostoichiometric internal stability (EIS) of nutrients accumulation and, concomitantly identified the main resistant regulating substances and their contributions to stress resistance of reed (Gramineae) in arid desert areas. Plants (digging method) and soil samples (quartering method)) obtained from sand dune (SD), desert steppe (DP), interdune lowland (IL), saline meadow (SM) and wetland (W) habitats were brought back to the lab for nutrients analysis. Results indicated that soil nutrients differed obviously, while reed maintained relatively stable ratios of SiO2: N, N: K, and P: K when the eco-environments changed in different habitats. Furthermore, reed exhibits common adaptive characteristics by mainly accumulating large amounts of SiO2 (122.6–174.0 g/kg) and NO3− (166.1–216.6 g/kg), as well as moderate levels of soluble sugar (SS: 24.0–55.0 g/kg), which are mainly stored in leaves for stress resistance. The contribution of ions to stress resistance was 80.03%–91.15% (with SiO2 and NO3− accounting for 54.91%–63.10%), whereas the contribution of solutes was only 8.85%–19.97% (with SS contributing to 5.14%–10.91%) in different habitats. These findings suggest that maintaining relatively high EIS, while still accumulating SiO2 and NO3− as main physiological regulators might be an effective strategy for reed to positively respond to adverse habitats, which provide a strong theoretical basis and technical reference for searching useful methods for restoration and reconstruction of the degraded ecosystems in desert oasis regions.

The Future behind the Mountains and the Sand Dunes

The Future behind the Mountains and the Sand Dunes

Enhancing the two-layer k-epsilon turbulence model through rough wall modification

Surface roughness significantly influences turbulence structures, affecting skin friction and velocity profiles. Precisely modeling the roughness effects is essential for reliable numerical simulation results in various engineering applications. This paper introduces enhancements to the two-layer k-epsilon (k−ε) turbulence model, incorporating surface roughness effects by adjusting variables in prescribed length scales and turbulent boundary conditions and ensuring the model switches between different roughness regimes. The accuracy of the enhanced model was validated using the Grigson–Colebrook type roughness function and experimental data from flat plate flows, as well as more complex geometries such as sand dune flow and ramp flow. The modified model demonstrated strong agreement with experimental data, accurately predicting the effects of roughness across diverse flow conditions, particularly in terms of velocity profiles. The proposed roughness modifications substantially improve the model's capability to simulate turbulent flows over rough surfaces, providing a valuable tool for predicting flow behavior in engineering applications involving rough surfaces.

Numerical Simulation of Gas-suspended Proppant Migration Based on Equivalent Principle

Abstract The gas-suspended proppant is composed of conventional proppant particles and hydrophobic aerophilic coating. The surface coating changes the surface wettability of the proppant and increases the adhesion of the proppant surface to the gas, changing the traditional liquid-carried proppant into a gas-carried proppant. The sand carrying capacity of low concentration polymer fracturing fluid can be greatly improved by using air-suspended proppant carrying technology. At present, there is no numerical simulation method aiming at the migration law of gas-suspended proppant. Based on the principle of equivalent substitution, the density of gas and particles is set as the calculated equivalent density during simulation. Similarly, the diameter of gas-suspended proppant is set as the calculated equivalent diameter during simulation. Then computational fluid dynamics software was used to simulate the Euler-Euler method. It is found that Euler-Euler method can simulate the placement of gas-suspended proppant in fractures. Compared with conventional proppant, gas-suspended proppant is not easy to settle during migration, and the settling sand bed still has fluidity and can be re-suspended. When gas suspension proppant density increases, the proppant sedimentation trend increased. Increase the injection rate of proppant, and the shape of long and high sand dunes will become shorter and lower. As the sand rate increases, the height of the sand bank rapidly increases.

Dolomite, quartzite, and sand indices defined for PRISMA hyperspectral data. Application to the Tamlalet inlier (Eastern High Atlas, Morocco)

The present work discusses the development of three novel spectral indices for PRISMA data. The Hyperspectral Dolomite Index (HDI) using B2320nm and B2349nm bands, the Hyperspectral Sand Index (HSI) based on the visible B515nm and B596nm bands, and the Hyperspectral Quartzite Index (HQI) using a combination of Relative Band Depths in B2167nm and B2206nm bands. The outputs of the three indices are grayscale images, where the brightest pixels represent the indices target. Applying HDI on PRISMA image of Tamlalet inlier (Moroccan Eastern High Atlas) led to discriminate the dolomites from lacustrine limestones and bare soils. HDI also suggests rectifying the local geological map by replacing limestones with dolomites in Jbel Ain Chair. HQI highlights quartz-rich rocks and provides better results than ASTER TIR indices. HSI can discriminate sand dunes from bare soils without being disturbed by vegetation. Dolomite, Quartzite, and Sand Hyperspectral indices show an overall accuracy of 91.2 %, 97.8 %, and 91.5 %, respectively. These indices could be adapted to other hyperspectral data having the required wavelengths.

The role of red sand dunes nano sized particles for improved oil recovery

The role of red sand dunes nano sized particles for improved oil recovery

Morphology of Sand Dune Fields in Al-Shehabi Area, Wasit Governorate

The present research is to identify the morphological kinds of sand dunes that are deposited in Al-Shehabi area in Wasit governorate, eastern part of Iraq. The main sand dunes that are determined in the studied area are symmetrical and asymmetrical barchans, nabkha, barchanoid ridges, and sand sheet dunes as seen in the field. Dimensions of barchan dunes are 1 - 8m high, and 3 -50m side dimension, and 3 - 25m length. Nabkha dunes’ dimensions ranges between 0.5m - 3m in length, and 0.5m – 2m high. In relation to the main wind direction in Iraq, these dunes face north-west to south-east. Barchanoid ridges, which are recognized in the studied area are with 6m in average height and accumulated by few barchan dunes. Sand sheet is also recognized in the studied area with small areal extension and with ripple marks.

Development of geopolymer and cement-based shotcrete mortar: Impact of mix design parameters and spraying process

Shotcrete mortar is used in various construction works, including repair, tunneling, mining, and slope stabilization, among others. Traditionally, cement is used to produce shotcrete mortars with high viscosity, flowability, and early strength. Geopolymers (GP) have the potential to replace cement in shotcrete mortars, owing to their ability to reduce the material’s environmental footprint without compromising performance. This investigation assesses the feasibility of utilizing fly ash and blast furnace slag-based GP mortars produced with dune sand in shotcrete applications while comparing them to cement-based mixtures. The GP and cement-based shotcrete mortars were designed to have similar yield stress values. The evaluated properties included the initial flow, thickness layer, rebound material, rheological properties, setting time, compressive strength, ultrasonic pulse velocity, and pull-off bonding strength. Test results showed direct relationships between the yield stress and initial flow values, as well as between the buildup thickness and plastic viscosity, revealing that GP mortars were suitable for shotcrete applications, specifically those produced with flow values of 18.5 cm or less. GP mixtures produced with higher slag content than fly ash, higher sand content compared to binder, higher SH molarity, and lower solution content achieved higher buildup thickness owing to their higher viscosity. In the second phase, the performance of four mixes with different initial flows was assessed at various pumping flow rates and distances between the wall and machine pipe nozzle. The findings confirmed that these spraying parameters are crucial to improve the shotcrete performance of GP mortar with varying fresh behaviors.

Trade-offs in the adaptation strategy of two dominant rhizomatous grasses to sand burial in arid sand dunes

Trade-offs in the adaptation strategy of two dominant rhizomatous grasses to sand burial in arid sand dunes

Vertical growth rate of planted vegetation controls dune growth on a sandy beach

The integration of coastal dunes planted with vegetation and dikes combines traditional infrastructure with dynamic aeolian sediment and ecological processes to enhance coastal resilience. The functioning of such dune-dike hybrid Nature-based Solution strongly depends on aeolian sediment transport and the vertical growth rate of vegetation. We used the AeoLiS numerical model to investigate the relative importance of aeolian and vegetation dynamics in the evolution of a 120 m long and 20 m wide marram grass-planted dune field on a Belgian sandy beach backed by a seawall, constructed in 2021. AeoLiS proved to be a promising tool for predicting these systems, effectively capturing aeolian sediment deposition, vegetation growth, and profile development three years post-construction. Seasonal variations in vegetation trapping efficiency, driven by sediment burial, and seasonal plant growth emerged as important factors controlling dune growth. Profile development discrepancies were attributed to unaccounted biotic and abiotic factors, highlighting the complexity of coastal eco-geomorphological processes. Dunes planted with vegetation wider than 20 m were identified to enhance sediment trapping without an increase in dune height. These findings offer actionable insights for coastal management, promoting strategic dune design and planting approaches to reinforce shoreline resilience. Additionally, the findings underscore the necessity for advancing eco-morphodynamic models and deepening our knowledge of coastal dune dynamics.

The meteoritic record of Arabia

Meteorites provide a wealth of information about the origin of the Earth and the solar system. Systematic searches have proved successful in cold and hot desert areas. Meteorite finds are favoured in areas with light-coloured surfaces that have been stable over tens of thousands of years and in hyper-arid climates. The deserts of Arabia are well suited for the search for meteorites. Following the first finds by explorers in the 1930s, and during oil exploration in the 1950s, a significant number of finds have been recorded in Oman since 1999, with more than 4000 meteorites currently recorded. Exploratory searches in Saudi Arabia have also shown a significant potential for meteorite discoveries. A collaborative Omani-Swiss search project was initiated in 2001 and 23 search campaigns since then have yielded more than 7300 samples, including meteorites from the Moon and Mars and, 37 strewn fields. Arabia has the potential to become one of the key regions for meteorite recovery and future research. Only three confirmed (Wabar, Saqqar and Jebel Waqf as Suwwan), several suspected and some dubious impact structures have been reported. The Wabar impact locality in Saudi Arabia features impact craters in dune sands, shocked and melted sand, and finds of several large meteorites.

Targeting Shallow Subsurface Sampling for Mars at Oxia Planum Using Fluvial Erosion–Deposition Modeling

A model-based surface fluvial erosion and deposition approach was adapted to Martian conditions to forecast the potential locations for shallow subsurface sampling by the Rosalind Franklin ExoMars rover at Oxia Planum. While remote and on-site images show only the surface visible features, former fluvial-related accumulation sites might be hidden. During the fluvial activity, most accumulation-related areas are interesting with regard to clay-like sediments, which could adsorb organics effectively—such sites could be identified by modeling. By applying the SIMWE fluvial erosion/deposition model, substantial variability in accumulation and deposition-dominated areas with their specific pattern and spatial distribution could be outlined, indicating that sophisticated targeting of future sampling could use such a model-based approach. At the main valley-like feature, former water flow tracks were identified, as well as deposition-dominated locations, which are the best targets for shallow subsurface sampling. Joint evaluation of safety aspects like slope angle and loose sand dunes with scientific aspects provide the best sampling locations. Such model-based targeting is important as by using only orbital images, these locations could not be identified.

A Critical Review of Eolian Ichnofacies

Two ichnofacies have been named to encompass inland eolian depositional systems, the Octopodichnus and the Entradichnus ichnofacies, and are often combined into a single, Octopodichnus–Entradichnus ichnofacies. In contrast, coastal dune fields are characterized by a mixture of traces produced by marine and nonmarine organisms attributed to a single, Psilonichnus ichnofacies. However, inland eolian depositional systems lack marine organisms and encompass multiple lithofacies, the most extensive and broadly defined as being dunal and interdunal (includes many water laid deposits). The two lithofacies host generally different ichnoassemblages. Dunes are dominated by arthropod and tetrapod walking traces, whereas interdunes are dominated by shallow burrows, though there is some overlap in the ichnoassemblages of both lithofacies. A re-evaluation of the three ichnotaxa unique to the Entradichnus ichnofacies indicates they are invalid: Entradichnus = Taenidium, Pustulichnus = Skolithos, and Digitichnus is not based on a biogenic structure. The Entradichnus ichnofacies is characterized by abundant horizontal, backfilled traces of mobile deposit feeders and other ichnotaxa that indicate it is a synonym of the Scoyenia ichnofacies. I advocate subsuming the Laoporus, Brasilichnium, and Chelichnus ichnofacies of earlier workers under the Octopodichnus ichnofacies. Thus, the two principal ichnofacies of eolian depositional systems are the Octopodichnus and Scoyenia ichnofacies, though several other ichnofacies have been identified. No single ichnofacies characterizes eolian depositional systems.

Spatio-temporal variation in mangrove crab diversity in five estuaries of Kerala, India

The present study investigated the community structure and faunal composition of mangrove crab assemblage of five estuaries in Kerala. Mangrove crabs were collected from different estuaries namely Puthuvype, Ayiramthengu, Dhalavapuram, Pullichira and Kottaramthuruth from January 2015 to December 2015. The numerical abundance was directly enumerated by handpicking crabs from the estuarial mangrove region from 100×100 cm quadrats from the estuarine mangrove regions. Thirteen brachyuran crab species were identified across the five estuaries, along with environmental and sedimentological parameters. Various diversity indices were calculated for spatial temporal comparisons. The study revealed that four of the estuaries exhibited similar crab species diversity, while Pullichira differed, displaying the lowest diversity due to habitat characteristics such as small islands or sand dunes and shallow depth. The calculated indices for species diversity, richness, dominance, evenness, taxonomic and phylogenetic relationships provide insights into the spatio-temporal variations of mangrove crab diversity. This study serves as a benchmark reference for future studies in these estuaries, and further monitoring and assessment of mangrove ecosystem health could support the development of ecosystem-based management strategies for deteriorating mangrove ecosystems.

Effect of adding dune sand to bituminous concrete intended for wearing courses

The 20th century was marked by the development of road infrastructure around the world, which necessitated a great need for pavement materials which in turn had to meet certain geotechnical criteria such as hardness, grain size and cleanliness. A traditional pavement body generally includes gravel, but unfortunately these materials are not available in some areas. From there was born the need to use local materials, such as tuff and dune sand, which exist in abundance and which are inexpensive and which have proven their effectiveness in road construction. The semi grained bituminous concrete SGBC intended for wearing layers, known by the name BC 0/14, generally is prepared by mixing two components: aggregates and bitumen. The design of this material considers several criteria related to one hand to the aggregates, namely mechanical characteristics, shape, and cleanliness of stones, the blue value of the fine, the particle size of the mixture (% passing through), the choice of the bitumen grade and mechanical performance as well the water resistance of asphalt concrete 0/14. The present work aims to study the influence of the substitution of the fraction 0/3 mm of the crushed sand (usually used in this type of materials) by fine dune sand, on the mechanical performance including Duriez and Marshall Stability and water resistance.

Monsoon control on evolution of the western Indian aeolian landscape: Insights from U-Pb detrital zircon geochronology and Sr-Nd-Hf isotope studies of the Thar Desert sand dunes

Evolution of landscape is linked to the interplay of tectonics, lithology, and climate. To better understand the evolution of aeolian landscape of the western Indian subcontinent and its major driver/s, we carried out a quantitative provenance analysis of the sand dunes of Thar Desert and desert river Luni using whole rock Sr-Nd-Hf isotopes and detrital zircon U-Pb geochronology. Our findings show Himalayan origin for the Thar sands. River Indus consistently contributed about 30–40 % of the total dune sand across the desert. The sand dunes in the north and the west of the desert are dominated by sediments derived from the source rocks drained by Sutlej river and its tributary Beas river whereas the dunes of central Thar are dominated by sediments supplied by rocks drained by Jhelum, Ravi and Chenab rivers. Analysis of detrital zircon U-Pb age spectra of sediments from desert river Luni reveal that dune sand of southern Thar Desert forms nearly 80 % of its present-day sediment load. Notably, the Thar dune sands show remarkable compositional similarity to the early to middle Holocene Indus delta sediments suggesting shared source/s. Existing paleolimnological and climatic records suggest a wetter environment in the Thar during early to middle Holocene. This evidence coupled with compositional similarities between the Thar dunes and the Indus delta sediments from the same period, indicate a probable extension of the Indus-Sutlej floodplain into southeast Thar during that time. Subsequent aridification of the region in the late Holocene likely led to seasonal winds recycling this fluvial sand to form the present-day Thar dunes, and shaping the current aeolian landscape in western India.